Recent studies have shown that the rate of potassium secretion in colon varies in response to metabolic needs of the organism to maintain potassium balance. The present study is concerned with the factors which govern the rate of potassium secretion at, and the cellular level, the mechanisms involved in translocation of potassium across the colonic epithelium. Since our data suggest that properties of potasssum transport are remarkably similar in large intestine and distal nephron in the kidney it is anticipated that these studies will provide important new insights into the processes concerned with potassium transport as a general biological phenomena as well as greater understanding of intestinal transport properties.